MB-10779 crash more informatively when receive wrong opaque

Change-Id: I8cdf6deeecfc6d9bc94faf4f441247e27ef25032
Reviewed-on: http://review.couchbase.org/35477
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
MB-10779 fix race during takeover

sometimes the response to ADD_STREAM(takeover) comes later than
both SET_VBUCKET_STATE responses. should block until both
ADD_STREAM and SET_VBUCKET_STATE responses arrive

Change-Id: I3e7d0b6c75edd41be2adbd9550db467ba6682ff5
Reviewed-on: http://review.couchbase.org/35478
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>